This invention relates to a method and system for controlling the final package weight of slug pack products using a computer-integrated control system. More particularly, this computer-integrated control system consists of the filing of the slug pack weights into a data storage and retrieval system for selection and final grouping of slug packs to form a final package weight. A designated number of slug packs, also sometimes known as stacks, is then selected for final packaging according to the individual slug pack weights combined to yield a final package within the desired weight range. If the slug packs are determined to be significantly underweight, or significantly overweight, a signal is sent to the length metering feeder whereby the number of articles to be wrapped in the slug pack is either increased or decreased in order to produce stacks having a weight falling within the desired range.
In many instances a package must contain a certain weight of product in order for it to meet various consumer protection laws. This is particularly the case with regard to foods such as crackers, cookies and similar items. It is always safe to put into each package a number of articles so that the packages will definitely meet the minimum weight requirement. However, when this is done, the producer is giving away, at no cost, a certain amount of the product. This may not seem to be significant when one, two or three extra crackers, cookies or similar items are put into each package in order to assure that the minimum weight is met. However, when it is considered that the manufacturer will produce several million packaged units, the inclusion of two or three extra items into each package results in the giving away, for free, several million of the individual food items. Consequently, it is the objective of each producer to meet the minimum weight requirement, but also not to significantly exceed this minimum weight requirement. In this regard various systems and equipment have been developed so that the items can be automatically packaged, the minimum weight requirement met, but the weight of each package not exceeding the minimum by more than a de minimis amount.
Automatic systems have been developed to produce packages having a final target weight. In U.S. Pat. No. 2,470,916 tuna fish is packaged into cans according to the weight of each piece of fish. The person doing the packing has a final target weight that must be met. Pieces of tuna fish of known weight are then chosen by the packer so that this final target weight can be met, but in a way that the target weight is not significantly exceeded.
In U.S. Pat. No. 3,939,928 varying numbers of items to be packaged are flowed to a set number of hoppers. The items in each hopper are then weighed. Knowing the weight of the items in each hopper and knowing the final target weight desired, the hoppers are chosen to fill a package so that the final weight of the items is above, but yet very close to, the target weight.
In U.S. Pat. No. 4,024,381 the objective is to have a certain number of biscuits or cookies packaged within a container. In order to accomplish this objective the items are conveyed to any one of a number of parallel-arranged counting channels. If the number of cookies within a counting channel is correct, the items in that channel are forwarded on for packaging or for stacking in combination with other items.
U.S. Pat. No. 4,545,179 is also directed to the packaging of cookies and similar items. In this patent a certain number of cookies are counted for packaging. This is accomplished by knowing the length of the desired number of cookies. If the cookies in various channels are of the correct length, they are then passed for packaging. If the number is not of the correct length, then the cookies are sent to a waste slot.
U.S. Pat. No. 4,164,260 discloses a method and apparatus for determining minimum and average weights prior to packaging so as to assure that no units are below a given minimum weight. If necessary, more of a product is added to a unit if it is below a desired minimum. If the deviation from the average weight is not acceptable, an alarm may be energized and the system shut down. Accumulators are used to store the new signals and the old signals. The signals are added algebraically to produce an output in accordance with total net deviation from the average. However, like the other references all processing is performed on a product prior to wrapping and packaging.
U.S. Pat. No. 4,398,229 discloses a device which is stated to be useful in packing articles such as cakes and candies in bags so that each package contains a set number of articles. This device is concerned with packing a certain number of articles and the final weight is not a concern.
In U.S. Pat. 4,537,229 there is disclosed an automatic weighing apparatus wherein two variables are sensed so that not only will the package have the proper weight, but also the correct volume. The two variables are weight and apparent specific gravity. Specific gravity is determined as a function of pressure by means of a pressure sensor. Foods such as potato chips and flaked cereals are mentioned as being suitable for packaging. In this technique there is no concern with regard to the number of articles packaged and all processing is prior to product wrapping.
U.S. Pat. 4,538,693 discloses a weighing apparatus. The product to be packaged is segregated into discrete quantities which are combined into a group that closely approximates a target weight. The product is then received by a number of discrete holding chambers. The weight in each holding chamber is known. A container is filled from the correct selection of chambers to get a desired total weight. However, as above noted, the articles are not pre-wrapped and all steps are conducted prior to any wrapping or packaging.
In U.S. Pat. No. 4,209,960 there is disclosed an apparatus for maintaining a constant weight of article stacks. A stack of cookies is produced by two stack forming devices' The cookies are received by the stack formers from a first conveyor. A second conveyor conveys the stacks away from the stack formers to a weighing machine and then on for packing in a carton. The weighing machine is connected electronically to the stack formers so that the length of the stack can be varied as a function of the stack weight. However, there is no wrapping of the stacks and then combining of the wrapped stacks by weight into a final package.
U.S. Pat. No. 3,557,889 discloses a process and apparatus for filling packages with granular or fluid material. A package is filled to an amount less than the desired weight. Product is added to the package from one or more hoppers containing a known weight of product until there is no weight deficiency.
U.S. Pat. No. 3,708,025 discloses a similar method and apparatus. The articles, such as oranges, are weighed and classified as to weight. A plurality of feeding channels deliver a set number of the weighed oranges to the end package in a manner so that a certain target weight is achieved.
U.S. Pat. No. 4,122,941 also discloses a similar method and but directed to the packaging of fish fillets. The fish fillets are fed onto weighing platforms. A computer knows the desired target weight and takes the fillets from the particular weight platforms in order to best meet the target weight. These fish fillets are then packaged. However here, as in U.S. Pat. No. 3,708,025 and U.S. Pat. No. 3,557,889, there is no forming of wrapped article stacks and then packaging chosen stacks in order to reach a desired target weight for the end package.
There are yet various other techniques for packaging items in order to meet a minimum weight requirement. However, none of these systems is directed to a technique where items such as cookies or crackers are prewrapped into stacks, the stacks weighed, and then the stacks chosen for final package in order to meet a minimum weight requirement but yet not to unduly exceed this weight requirement. Also not used by others is the technique whereby if the wrapped stacks do not meet a desired weight then the length of the grouping of cookies or crackers incorporated to produce each stack is changed. These stacks are then forwarded for subsequent selecting and combining of stacks. In this way, overweights are reduced and the weight requirements are met.